A "gaming bucket" is some sort of medium-sized container, jokingly, said to be used during long gaming sessions (4+ hours) in place of restroom breaks. This phrase was semi popular among some MMO gamers at one time.

Three guild members in a guild raid in an MMO:

<Shanksalot> "Hey guys, can we take a five minute bio after this boss?"
<Meatshield> "Whoa whoa whoa! We just took a bio break at the midpoint, why didn't you go then?"
<Shanksalot> "Uh...I didn't have to??"
<Omgwtfkill> "RAID FOUL!! Use your gaming bucket, pansy! lol"
<Omgwtfkill> "Gaming Bucket: Get it. Use it. Love it."
<Meatshield> "Kill...you're disgusting. o.o"
<Shanksalot> "..."